the garbled text that is the result of text being decoded using an unintended character encoding.

Wikipedia by way of Hacker News, where I learned:

In Russian this phenomenon is called “бНОПНЯ” (read “b-nop-nya”) and was caused by taking the word “Вопрос” (meaning: “question”) in win-1251 encoding and reading it as if it was in KOI-8 encoding.

Also this is called “крокозябры” (read: kro-ko-zya-bry, nonsense word, no translation) especially when reading a binary file in a text viewer.